1. Field of the Invention
The present invention relates to a vibration generator for use in a portable terminal or the like. More specifically, the present invention pertains to a vibration generator in which a vibrating body reciprocatingly vibrated by magnetic fields is supported by a leaf spring.
2. Description of the Related Art
A portable terminal such as a cellular phone or the like includes a vibration generator capable of notifying a user of arrival of an incoming call. Different types of vibration generators have heretofore been developed. For example, there is known a vibration generator in which an eccentric weight is attached to a rotating shaft. The vibration generator of this type generates vibrations by rotating the eccentric weight with a motor. In the vibration generator of this type, it is however difficult to reduce the thickness thereof. Moreover, the vibration generator of this type suffers from problems in that the vibration generator is low in durability and tends to generate noises during a long-time use.
As a solution to these problems, there is available a vibration generator that reciprocatingly vibrates a vibrating body using the magnetic fields formed by a coil and a magnet.
Japanese Patent Application Publication No. 2002-200460 discloses a technology on a vibration actuator. The vibration actuator includes a fixing portion serving as a cover; a vibrating body having a plurality of magnets and a yoke for closing the magnetic fluxes generated by the magnets; a plurality of elastic members for movably holding the vibrating body in the fixing portion; and a coil for generating a thrust force between the fixing portion and the vibrating body to make the vibrating body vibrate in a specified vibration direction by flowing an electric current in a direction to interlink with the magnetic flux generated by the magnets.
In the technology disclosed in Japanese Patent Application Publication No. 2002-200460, the vibrating body is held by the elastic members arranged at the opposite sides of the vibrating body in the vibration direction of the vibrating body. Each of the elastic members is formed by joining one longitudinal ends of two band-like leaf springs and bending the leaf springs from the joint portion at an acute angle. Alternatively, each of the elastic members may be formed by bending the longitudinal intermediate portion of a single band-like leaf spring.
PCT Patent Application Publication No. 2010/026883 discloses a technology on a linear motor and a cellular phone employing the linear motor. The linear motor includes a spiral coil and a vibrating body arranged in an opposing relationship with the spiral coil. The spiral coil includes a first portion extending in a direction orthogonal to the moving direction of the vibrating body and a second portion extending parallel to the moving direction of the vibrating body. The magnitude of the magnetic fluxes formed by the first portion is larger than the magnitude of the magnetic fluxes formed by the second portion.
In the technology disclosed in PCT Patent Application Publication No. 2010/026883, the vibrating body is held by leaf springs bent at an acute angle and arranged at the opposite sides of the vibrating body in the vibration direction of the vibrating body.
U.S. Patent Application Publication Nos. 2010/0213773 and 2011/0089772 discloses a technology on a linear vibrator. The linear vibrator includes a housing, a vibrating body supported by an elastic member, and a coil arranged within the housing.
The elastic member disclosed in U.S. Patent Application Publication No. 2010/0213773 includes an attachment portion attached to a circumferential wall portion and an arm portion provided with a holding portion. The attachment portion and the holding portion are arranged parallel to each other and are connected to each other by a U-like connecting portion. In the elastic member disclosed in U.S. Patent Application Publication No. 2011/0089772, a holding portion is detachably attached to an arm portion.
In the leaf spring structures disclosed in Japanese Patent Application Publication No. 2002-200460 and PCT Patent Application Publication No. 2010/026883, however, large stresses are generated in the portions of the leaf springs bent at an acute angle. For that reason, if the leaf springs work for a long period of time, the leaf springs may possibly be destroyed due to fatigue.
The elastic members disclosed in U.S. Patent Application Publication Nos. 2010/0213773 and 2011/0089772 are structurally complex and costly to manufacture.